Multi-branch fitting made of composite material and method of manufacturing such a mult-branch fitting

ABSTRACT

A multi-branch fitting includes at least three branches, molded from a composite material and, more precisely, from a fiber-reinforced thermoplastic or thermoset matrix. The fitting is intended for assembling components which are at an angle to one another. There are at least three flat or substantially flat branches or flanges extending radially from a joining zone, and at least one face or part of a face constituting a bearing face for one or more of the components that are to be attached. The joining zone has a cross section, in the transverse direction, in the shape of a polygon with concave sides. The connection of each of the branches or flanges with another adjacent branch or flange is achieved through a portion in the shape of a curved blade which gives the joining zone one of its concave shapes.

RELATED U.S. APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in the field of the composite materials,to a multi-branch fitting, comprising at least three branches aimed atassembling parts forming an angle between them, as well as to a methodfor manufacturing such a multi-branch fitting.

Under multi-branch fitting, it is understood that a fitting comprises atleast three flat or substantially flat branches or flanges extendingradially from a joining area. The branches or flanges of thesemulti-branch fittings may not necessarily all be intersecting accordingto one and the same axis, and extend according to planes intersectingexternally to the fitting. The most often used multi-branch fittings areparticular cases such as T-, Y- or X-shaped fittings.

A multi-branch fitting made of composite material is essentially, butnot restrictively, aimed at being used in the field of aeronautics, forexample to connect two or more parts, and as a replacement for similarfittings hitherto made of metal. These fittings are aimed at being madeintegral with the parts to be connected and therefore provided,externally to the folding, with coupling areas aimed at permitting theassembling of said parts to be connected, in association with means formaking integral, which may consist, non-restrictively, of gluing,riveting or screwing means.

2. Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 37 CFR 1.98

By way of an example, a multi-branch fitting of the state of thetechnique, in this case a T-shaped fitting, is shown in FIG. 1. ThisT-shaped fitting 1 includes a sole 10, in the form of a plate, and atransverse wall 11, which extends on one side 12 of said sole 10 whileforming with the latter an angle, in this case a right angle, and whichdivides said sole into two parts 13 and 14, in this case having the samedimensions, the side of said sole opposite the one from which extendssaid transverse wall constituting a bearing face 15 aimed at enteringinto contact with one of the parts to be fixed, while either one of thetwo faces 16 and 17 of said transverse wall 11 constitutes a bearingface for one or several other parts to be fixed. This T-shaped fitting 1includes a multiplicity of holes 18 aimed at permitting to fix the partsto be assembled, through joining means such as screws or rivets. Such aT-shaped fitting 1 is achieved by molding a composite material, morespecifically from a fiber-reinforced thermoplastic or thermosettingmatrix.

The replacement of the metallic elements by elements made of compositematerial is essentially imposed by the necessity of a weight gain. Thishas however drawbacks from the point of view of the strength.

It is indeed known that the weak point of the composite materials is thematrix, which has a much lower specific strength than the fibers. Therange is for example of 20 MPa for resin and of 4000 Mpa for carbonfiber. Therefore, the collapsing of a part made of composite material isgenerally due to a breaking of the resin connecting the fibers, and inthe case of a T-shaped fitting made of composite material the breakingis observed during a work essentially of unfolding and folding thetransverse wall relative to the sole.

In order to cope with this drawback, it would be appropriate that thereinforcing fibers are subjected to the tensile and/or compressionforces, and that the resin is not or little stressed. It is however notpossible with the presently known techniques to achieve an optimalorientation of the fibers in such a part, except at a very high cost.

From W02010072952 is known an L-shaped fitting, made by molding acomposite material, which comprises two portions forming an anglebetween them and drilled with holes in order to permit to make bothportions integral by fastening means, at least one of said two portionshaving, on the inner side of said fitting, a concave curved profile, andmore particularly a spherical or cylindrical profile, the hole or holesprovided in same having an axis radial to the curvature.

This configuration permits the reinforcing fibers, or part of them, tobe oriented in the direction of traction and/or compression, so thatthey are stressed by priority with respect to the resin.

However, such an L-shaped fitting cannot substitute a multi-branchfitting for assembling parts forming an angle between them; it does nothave the required rigidity both for folding and unfolding. In order toreplace for example a T-shaped fitting, two of these L-shaped fittingsshould then be used, as preconized in said WO2010072952, with thedrawback of an uneasy implementation and an obvious failure of unicityof the part, resulting into an additional weight.

SUMMARY OF THE INVENTION

The present invention is aimed at providing a multi-branch fitting madeof composite material aimed at connecting parts forming an angle betweenthem and permitting to solve the various above-mentioned drawbacks, aswell as the method for manufacturing such a multi-branch fitting.

The multi-branch fitting, comprising at least three branches, made bymolding a composite material, and more specifically a fiber-reinforcedthermoplastic or thermosetting matrix, aimed at assembling parts formingan angle between them, according to the invention, comprising at leastthree flat or substantially flat branches or flanges extending radiallyfrom a joining area, and at least one face or face portion of which isshaped so as to constitute a bearing face for one or several of saidparts to be fixed, is characterized in that, on the one hand, saidjoining area has a cross-section, in the transverse direction, i.e.perpendicular to at least one of said branches or flanges, having theform of a polygon with concave sides and, on the other, in that theconnection of each one of said branches or flanges to another adjacentbranch or flange, is made through a portion having the form of a curvedblade that provides said joining area with its concave shapes.

According to an additional feature of the multi-branch fitting of theinvention, the joining area has, in addition to its concave profile atthe level of the joining of two adjacent branches or flanges, asuccession, in its longitudinal direction, of domed or hollow portions.

According to another additional feature of the multi-branch fitting ofthe invention, the flanges or branches include, at the level of theirportions forming bearing faces, holes for the passing through of joiningmeans.

According to a particular embodiment of the multi-branch fittingaccording to the invention, it has a T-shaped profile and thus includesa sole being in the form of a plate, and a transverse wall, whichextends on one side of said sole, forming an angle with the latter andwhich divides said sole into two portions, the side of said sole,opposite the one on which said transverse wall extends, constitutingentirely or partially a bearing face aimed at entering into contact withone of said parts to be fixed, while either one of both faces of saidtransverse wall constitutes entirely or partially a bearing face for oneor several other ones of said parts to be fixed, said sole and saidtransverse wall being designed capable of cooperating with means formaking integral the joining area of said transverse wall with that ofsaid sole having a traverse cross-section, in the directionperpendicular to the plane of said transverse wall, in the form of atriangle with concave sides, while the connection of said transversewall to each of said two portions is made through a portion in the formof a curved blade.

The method for manufacturing a multi-branch fitting made of compositematerial, as defined above, is essentially characterized in that itconsists in:

-   -   assembling as many parts to each other as there are branches or        flanges, each of said parts being a part aimed at constituting a        portion, in the direction of the thickness, of a branch or        flange, and a portion, in the direction of the thickness, of an        adjacent branch or flange and, on the other hand, folded        according to a radius of curvature in order to form an angle        said adjacent branches or flanges must form between them,    -   arranging in the joining area, into contact with said parts, a        core, whether durable or not, perfectly matching the shapes of        said parts, and    -   finally arranging the assembly obtained in a mold and applying        particular pressure and/or temperature conditions, so as to        carry out the polymerization of said composite material.

According to an additional feature of the inventive method, it comprisespreviously the following operations:

-   -   preparing layers of composite material each formed of a matrix,        in which one-directionally arranged fibers are embedded, in        order to create the parts to be assembled, and    -   shaping said layers through curved folding, concentrically to an        axis perpendicular to the orientation of said fibers.

According to another additional feature of the inventive method, itcomprises in addition, during the shaping of the layers of compositematerial, the following operations:

-   -   making, in the folding area, for each part, in the longitudinal        direction of the folding axis, a succession of hollow or domed        portions, which are arranged symmetrically with respect to those        created in the folding area of the adjacent parts, so as to        permit an encasing during the nearing back-to-back to each other        of said parts.

According to a particular embodiment of the inventive method, itconsists, for manufacturing a T-shaped multi-branch fitting, in:

-   -   assembling three parts, namely two L-shaped parts, the folding        area of which is curved, assembled so that one branch or flange        of one of them is into contact with a branch or flange of the        other one, and so that the other two branches or flanges are in        the extension of each other, and a globally flat third part        arranged in contact with said two branches or flanges in the        extension of each other, and having, in front of the joining        area of said two branches or flanges, a portion domed towards        said joining area.

According to an additional feature of the particular embodiment of theinventive method, it comprises previously the following operations:

-   -   shaping of a first layer of composite material formed of a        matrix, in which one-directionally arranged fibers are embedded,        in order to create the first L-shaped part, the curved folding        area of which is concentric to an axis perpendicular to the        orientation of said fibers, and which has, in the longitudinal        direction of said axis, a succession of hollow or domed        portions,    -   shaping of a second layer of composite material formed of a        matrix, in which one-directionally arranged fibers are embedded,        in order to create the second L-shaped part, the curved folding        area of which is concentric to an axis perpendicular to the        orientation of said fibers, and which has, in the longitudinal        direction of said axis, a succession of hollow or domed        portions, which are arranged symmetrically with respect to those        created in said first layer, so as to permit an encasing during        the nearing back-to-back to each other of said L-shaped parts,        and    -   shaping of a third layer of composite material formed of a        matrix, in which one-directionally arranged fibers are embedded,        in order to create the third globally flat part, which has in        its median region a domed transverse area, along which is        provided a succession of hollow and domed portions capable of        closely cooperating in encasement with the hollow and domed        portions the portions of said L-shaped parts include, which said        third part is aimed at entering into contact with.

It should be noted that the manufacturing method can have numerousvariants, namely depending on the molding techniques being used.

Thus, for example in the case of using a molding method by injection ofresin on a preformed mat, of the RTM (Resin Transfer Molding) type, itis possible to use this technique either for making the parts to beassembled in substitution of the shaping of layers or for molding thepart integrally by injection of resin, while the mold incorporates thepreformed mat and the core that guarantees the positioning of thereinforcing fibers.

The advantages and features of the multi-branch fitting and themanufacturing method according to the invention will become clear fromthe following description, which refers to the attached drawing, whichrepresents a non-restrictive embodiment of same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a schematic perspective view of a T-shaped fitting ofthe state of the art.

FIG. 2 represents a schematic perspective view of a T-shaped fittingaccording to the invention.

FIG. 3 represents a schematic perspective view of the same T-shapedfitting during its manufacture.

FIG. 4 represents a schematic side elevation view of the same T-shapedfitting during its manufacture.

FIG. 5 represents a schematic perspective and cross-sectional viewaccording to the axis XX′ of FIG. 4.

FIG. 6 represents a schematic perspective and cross-sectional viewaccording to plane YY′ of FIG. 4.

FIG. 7 represents a schematic perspective view of a portion of the sameT-shaped fitting according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

For the sake of simplification, the following description refers only toa T-shaped multi-branch fitting, knowing that other configurations arepossible.

When referring to FIG. 2, one can see a T-shaped fitting 2 according tothe invention, which comprises a sole 3 topped by a transverse wall 4.

The sole 3 has a globally flat shape, the side opposite the one, fromwhich the transverse wall 4 extends, constitutes a bearing face 30 aimedat entering into contact with one of the parts, not shown, to beassembled.

The transverse wall 4 extends perpendicularly to the sole 3, and dividesthe latter into two portions 31 and 32 having the same dimensions. Thewall or branch 4 has face portions 41 and 42. Similarly, the twoportions or branches 31 and 32 can have face portions 31 a, 31 b and 32a, 32 b.

It should be noted that this architecture constitutes a particularembodiment, and that it is perfectly possible that the transverse wall 4forms with the sole 3 an angle other than a right angle, and/or thatthis transverse wall 4 divides the sole 3 into two portions havingdifferent dimensions.

Likewise, the sole 3 can have a folding, for example in front of thewall 4, so as to obtain a Y-shaped multi-branch fitting, while anothertransverse wall can extend from the bearing face 30 of the sole 3, inorder to obtain an X-shaped multi-branch fitting.

The transverse wall 4 has a free extreme portion 40, both sides 41 and42 of which are flat, so as to be able to constitute contact faces withone or several parts to be assembled.

The joining of the T-shaped fitting 2 and the parts to be assembled canoccur in different ways, non-restrictively through gluing, screwing orriveting, in this case the sole 3 and the transverse wall 4 includeholes 33 and 43, respectively, permitting the passing through of screwsor rivets, not shown.

The transverse wall 4 is made integral with the sole 3 through a joiningarea 20, which has a triangle-shaped transverse cross-section, in thedirection perpendicular to the plane of the transverse wall 4, the threesides of which are concave. Thus, the connection between the wall 4 andthe portion 31 of the sole 3 is made by means of a concave curved blade21 globally concentric to an axis R, while the connection between thewall 4 and the portion 32 of the sole 3 is made by means of a concavecurved blade 22 globally concentric to an axis S, and the face 30 of thesole 3 has, in front of the transverse wall 4, a concave recess 34. Eachcurved blade portion 21 has a first connecting edge 21 a attached to onebranch 4, a second connecting edge 21 b attached to one adjacent branch31, and a folded spine portion 21 c.

One should note the presence between the blades 21 and 22 and the sole3, of a core 23, which, as will be seen below, is indispensable only forthe manufacture.

The concave shape of the blade 21 participates to the strength duringthe unfolding of the transverse wall 4 with respect to the portion 31 ofthe sole 3 and, hence, during the folding of the wall 4 onto the portion32 of the sole 3, while the blade lame 22 participates to the strengthduring the unfolding of the transverse wall 4 with respect to theportion 32 and, hence, during the folding of the wall 4 onto the portion31.

It should be noted that the concave recess 34 of the sole 3 helpsincreasing the strength during the folding and the unfolding.

This strength during the folding and the unfolding is increased by thepresence of undulations resulting from deformations formed, at the levelof the joining area 20, of a succession, in the longitudinal directionof the joining area 20, of alternated domed 24 and hollow 25 portions.

These domed and hollow portions are essentially created at the level ofthe blades 21 and 22, and symmetrically to each other, as will be seenbelow.

When referring now to FIGS. 3, 4, 5 and 6, one can see the same T-shapedfitting 2, before the polymerization phase permitting to obtain theT-shaped fitting 2 as shown in FIG. 2.

In FIG. 3 can be seen that the T-shaped fitting 2 results from theprevious assembling of three parts, namely two L-shaped parts 5 and 6,and one globally flat part 7.

The L-shaped part 5 includes two flanges 50 and 51 connected by a curvedfolding area 52 concentric to the axis R, while the L-shaped part 6includes two flanges 60 and 61 connected by a curved folding area 62concentric to the axis S.

Both L-shaped parts 5 and 6 each result from the shaping of a layer ofcomposite material formed of a matrix, in which fibers are embeddedarranged one-directionally in the direction perpendicular to the line offolding, so that these fibers are wound concentrically to the axes R andS, respectively.

As can be seen in FIGS. 5 and 6, the L-shaped parts 5 and 6 alsoinclude, essentially at the level of the folding area 52 and 62,deformations, namely for the L-shaped part 5, a median pit 53 edged bytwo bosses 54, and for the L-shaped part 6, a median boss 63 edged bytwo pits 64.

The two L-shaped parts are assembled back-to-back, i.e. the flanges 51and 61 are placed against each other, while the flanges 50 and 60 are inthe extension of each other, with a perfect matching of the median pit53 with the median boss 63, and of the pit 64 with the bosses 54.

The globally flat part 7 completes the assembly by being applied againstthe flanges 50 and 60. This part 7 also results from the shaping of alayer of composite material formed of a matrix, in which fibers arrangedone-directionally in the direction parallel to that of the fibers of theparts 50 and 60 are embedded.

The part 7 has in its median region a domed transverse area 70, aimed atbeing placed, during the assembling, in front of the joining of theL-shaped parts 5 and 6. This domed transverse part 70 includes inaddition deformations, namely pits 71 and bosses 72, visible in FIG. 5,aimed at cooperating en encasement with the pits 53 and 64, and thebosses 54 and 63 of the flanges 50 and 60.

It will be understood that the assembling of the flanges 51 and 61 isaimed at constituting, after molding, the transverse wall 4 of theT-shaped fitting 2, while the assembling of the flanges 50 and 60 withthe part 7 is aimed at constituting the sole 3, and that the foldingareas 52 and 62 are aimed at constituting the blades 21 and 22,respectively.

It should be noted that the assembling is complemented by previouslyplacing a core 23, represented in FIG. 7, which is designed capable ofclosely encasing between the parts 5, 6 and 7, so that the latterpreserve, during the molding operation until the polymerization, theirinitial shapes, and especially so as to guarantee the optimized radiusof curvature of the folding areas 52 and 62 and, hence, of thereinforcing fibers they contain.

The core 23 is indispensable for the molding operation, it thus permitsthat no sagging of the parts 5 and 6 onto the part 7 occurs at the levelof the folding areas. On the other hand, it is not indispensable forusing the T-shaped fitting 2, it can therefore consists,non-restrictively, of an inflatable bladder, of a part of elastomerremovable after molding, or of a part made of fusible material.

The T-shaped fitting 2 permits to optimize the use of the reinforcingfibers the layers of composite material being used contain. Because ofthe concave curved shape of the blades 21 and 22, shape that the fibersfollow, the forces during the unfolding are borne almost to a largeextent by these fibers.

The deformations 53, 54, 63 and 64 permit to create the domed 24 andhollow 25 portions and, hence to increase the strength of the T-shapedfitting 2, while preserving a constant thickness of the walls of theT-shaped fitting 2 and, hence, without increasing its weight.

What is claimed:
 1. A multi-branch fitting formed by molding layers of acomposite material, the fitting comprising: a plurality of at leastthree flanged fitting parts, each fitting part formed by folding a layerof composite material and comprising a pair of substantially planarflanges connected at an angle along respective longitudinal edgesthereof by a curved folded spine portion, each respective flange beingjoined to a flange of another one of the plurality of fitting parts;wherein corresponding flanges of adjacent fitting parts are joinedback-to-back against each other to form a plurality of at least threebranches radially extending from an enclosed joining area comprisingconcave sides defined by the curved spine portions of the fitting parts,each branch being generally flat and having a first face portion definedby a first respective flange and an opposing second face portion definedby a second respective flange, each face portion comprising a pluralityof holes extending therethrough for receiving attachment fasteners, eachbranch forming a branch angle with an adjacent branch; wherein a foldangle between the flanges of each fitting part corresponds to arespective branch angle between adjacent branches; wherein the foldedspine portion of each fitting part comprises undulations extending alonga longitudinal direction of the spine portion, the undulations definedby at least a first domed portion and a first hollow portion, each domedportion being convex facing outward toward respective branches andoutward from a longitudinal axis of the joining area, and each hollowportion being concave facing away from respective branches and inwardtoward the longitudinal axis of the joining area; and whereincorresponding flanges of adjacent fitting parts are assembledback-to-back against each other such that each hollow portion of a firstrespective fitting part is matingly received within a correspondingdomed portion of a second respective fitting part.
 2. The multi-branchfitting according to claim 1, wherein each folded spine portioncomprises at least two domed portions aligned along the folded spineportion with a respective hollow portion disposed between each pair ofadjacent domed portions.
 3. The multi-branch fitting according to claim1, wherein the branch angle between two adjacent branches is generally180 degrees so as to form a plane, and wherein the branch angle betweena respective third branch and each of the two adjacent branches isgenerally 90 degrees, said respective third branch being transverse tosaid plane, said joining area having a T-shaped cross-section.
 4. Amethod for manufacturing a multi-branch fitting according to claim 1,the method comprising the steps of: folding a respective layer ofcomposite material to form each of the plurality of fitting parts, usinga core disposed between layers of composite material forming the fittingparts to form said respective curved folded spine portions; setting thelayers of composite material defining the fitting parts in a mold; andpolymerizing the fitting parts under pressure and at temperatures to setthe composite material.
 5. The method for manufacturing according toclaim 4, wherein the step of folding a respective layer of compositematerial to form each of the fitting parts, further comprises: arrangingfibers in one direction; embedding the fibers in a matrix so as to forma layer of composite material; and folding said layer of compositematerial concentrically around axes perpendicular to said one directionof fibers so as to form each fitting part.
 6. The method formanufacturing according to claim 4, wherein the branch angle between twoadjacent branches is generally 180 degrees so as to form a plane, andwherein the branch angle between a respective third branch and each ofthe two adjacent branches is generally 90 degrees, said respective thirdbranch being transverse to said plane, said joining area having aT-shaped cross-section; wherein two fitting parts are L-shaped; whereinone fitting part is flat; and wherein said third branch is formed bysaid two fitting parts being L-shaped.
 7. The method for manufacturingaccording to claim 4, wherein the step of folding a respective layer ofcomposite material to form each of the fitting parts, further comprises:arranging fibers in one direction; embedding the fibers in a matrix soas to form a layer of composite material; folding said layer ofcomposite material concentrically around axes perpendicular to said onedirection of fibers so as to form each fitting part; folding arespective folding area of said layer of composite material over arespective domed folding portion of a core so as to form said domedportion; and folding said respective folding area of said layer ofcomposite material over a respective hollow folding portion of a core soas to form said hollow portion.